1. Field of the Invention
This invention relates to a continuous mining machine and, more particularly, to a mining machine having a cutter drum drive assembly that includes input drive shafts for transmitting rotation to a pair of canted end drum sections and to an intermediate drum section to rotate a drum assembly at a preselected speed for reduced dust generation while dislodging mine material in a manner that extends the operating life of the drive assembly.
2. Description of the Prior Art
Continuous mining machines, as illustrated in the U.S. Pat. No. 3,774,969, are utilized in underground mining operations to continuously dislodge solid material from the face of a mine shaft. A boom member extends forwardly from an elongated body portion of the mining machine that is propelled through the mine on endless crawler tracks. The boom member is pivotally connected to the mining machine body portion and rotatably supports a cutter drum assembly having peripherally extending elements. The cutter drum assembly extends transversely to the longitudinal axis of the body portion and, upon rotation, the cutting elements dislodge solid material from the mine face.
The cutter drum assembly is pivoted through an arcuate vertical path and sumped into the mine face to make a shear cut in the mine face. The dislodged material is fed rearwardly onto a gathering platform having suitable gathering devices which direct the dislodged material rearwardly onto a conveyor that extends longitudinally on the mining machine to transport the material toward the rear of the mining machine. By dislodging mineral material from the mine face in this manner, a mine passageway or room is formed to thus permit the mining machine to advance and continuously dislodge material from the mine face.
Full face drum-type mining machines, as illustrated in U.S. Pat. No. 3,305,273, include support means and drive means for the drum. The support and drive means include fixed annular end portions of the boom member extending around the external surface of the drum. Endless chain elements with cutter bits mounted thereon extend around the support means to dislodge material from the mine face along the width of the annular end portions of the supporting boom.
As disclosed in U.S. Pat No. 3,774,969, the drum member has an intermediate drum section and canted end drum sections with rear openings between the inner ends of the end drum sections and the outer ends of the intermediate drum section. Input shafts extend through these openings and each input shaft includes at its outer end a drive pinion meshing with a bevel gear rotatably supported within the intermediate drum section. The bevel gear is splined to a shaft with a sun gear of a planetary gear train nonrotatably mounted thereon. Planet gears of the planetary gear train are secured to the intermediate drum section and are rotated by the driven sun gear. The planet gears are also connected through universal joints to the adjacent canted end drum section.
The above described arrangement of transferring rotation from the intermediate drum section through a planetary gear train to the end drum sections requires a relatively large diameter intermediate drum section in order to accommodate the planetary gearing. This type of drum drive is particularly adaptable to mining operations were the mineral seam to be mined is relatively thick. Consequently, a mining machine drum drive arrangement with a planetary gear train in the intermediate drum section is not desirable for thin seam mining operations.
U.S. Pat. Nos. 3,774,969 and 3,848,930 are further examples of drum drive arrangements in which the intermediate drum section transmits rotation to the canted end drum sections. The canted end drum sections extend outwardly at an angle with respect to the intermediate drum section so that end drum drive shafts are not axially aligned with the intermediate drum drive shafts. The input drive shafts extend from the drive motors in parallel relation to the longitudinal axis of the mining machine. Because the end drum sections are canted outwardly, the end drum drive shafts are positioned at an angle greater than 90.degree. with respect to the input drive shafts.
U.S. Pat. No. 4,270,803 discloses a single planetary gear train positioned in each canted end drum section rather than in the intermediate drum section. With this arrangement, rotation is transmitted from the end drum sections to the intermediate section rather than from the intermediate section to the end drum sections. This arrangement permits a reduction in the diameter of the intermediate drum section to provide a more efficient dislodging operation for thin seam mining. Another advantage of this arrangement is the increased clearance provided around the intermediate drum section for the flow of dislodged material onto the gathering platform. Also, a smaller base diameter for the intermediate drum section is known to substantially prevent clogging of dislodged material between the mine face and the intermediate drum section.
One of the results of positioning a planetary gear train in the end drum sections in order to reduce the base diameter of the intermediate drum section is higher rotational speeds of the intermediate drum section and the end drum sections. This has the advantage of dislodging material from the mine face at a greater rate for increased productivity of the mining machine. However, dislodging material at an increased rate generates more dust, which is circulated in the mine atmosphere and particularly at the mine face in coal mining operations. The suppression of the generation of respirable dust in the mine atmosphere as a result of the mining operation has become the subject of increased federal regulation in the area of mine health and safety.
Another consequential result of rotating the cutter drum at an increased rotational speed by the provision of a planetary gear train in the end drum section is increased wear of the drive components, particularly the drive components which transfer the drive from the end drum sections to the intermediate drum section. Wear of drive components is a problem, particularly at the point of coupling the drive from the planetary gear train to the end drum section and to the end drum drive shaft that rotates the end drum section. When the rotating cutter drum is subjected to overload conditions, wear of these components is accelerated. Consequently, replacement of these worn drive components is costly in the terms of lost productivity due to downtime.
While it has been suggested to provide a mining machine cutter drum drive for transmitting rotation by a planetary gear train from canted end drum sections to the intermediate end drum section, the known devices generate undesirable concentrations of respirable dust in their mining operation. Also, accelerated wear of the drive components of the canted end drum sections is encountered as a result of operating this type of cutter drum assembly at a higher rotational speed. Therefore, there is a need for a cutter drum having canted end sections that utilizes a planetary gear train operable to transmit rotation form the end drum sections to the intermediate drum section at a rotational speed for a desired rate of dislodging material from the mine face while reducing the concentration of respirable dust normally generated in the mine atmosphere and for reducing the wear on the drive components to extend the operating life of the drum drive assembly.